#14060: Improve minimal_quadratic_twist()
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       Reporter:  cremona          |        Owner:  cremona
           Type:  defect           |       Status:  new
       Priority:  major            |    Milestone:  sage-6.1
      Component:  elliptic curves  |   Resolution:
       Keywords:  pari precision   |    Merged in:
        Authors:                   |    Reviewers:
Report Upstream:  N/A              |  Work issues:
         Branch:                   |       Commit:
   Dependencies:                   |     Stopgaps:
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Changes (by cremona):

 * cc: wuthrich (added)


Comment:

 I see two possibilities here:  either rename this function
 {{{minimal_twist()}}} and return (as it does now) a curve which may be a
 sextic or quartic twist when j=0 or j=1728;   or keep this name and be
 more restrictive for those j-invariants so that the returned curve
 literally is a quadratic twist.  A third possibility is to have both named
 functions, doing the same thing unless j=0 or j=1728.

 I am CC-ing Chris W since the only place where this function is used
 (according to {{{search_src()}}}) is in {{{sha_tate.py}}}, line 540, and
 whatever we do must be compatible with what is needed there!

 Of course this is in addition to adding one line to return self of
 {{{self.conductor().is_squarefree()}}}.

--
Ticket URL: <http://trac.sagemath.org/ticket/14060#comment:3>
Sage <http://www.sagemath.org>
Sage: Creating a Viable Open Source Alternative to Magma, Maple, Mathematica, 
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